scholarly journals Assessing the impact of ground-motion variability and uncertainty on empirical fragility curves

2015 ◽  
Vol 69 ◽  
pp. 83-92 ◽  
Author(s):  
Ioanna Ioannou ◽  
John Douglas ◽  
Tiziana Rossetto
Keyword(s):  
Ground Motion ◽  
Fragility Curves ◽  
Ground Motion Variability ◽  
The Impact

scholarly journals SEISMIC DAMAGE SCENARIOS IN KALAMATA (S. GREECE)

2017 ◽  
Vol 50 (3) ◽  
pp. 1495
Author(s):  
D. Kazantzidou-Firtinidou ◽  
I. Kassaras ◽  
A. Ganas ◽  
C. Tsimi ◽  
N. Sakellariou ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Fragility Curves ◽  
Site Amplification ◽  
Soil Conditions ◽  
Damage Scenarios ◽  
Local Soil ◽  
Protection Strategies ◽  
The Impact ◽  
The City

Damage scenarios are necessary tools for stakeholders, in order to prepare protection strategies and a total emergency post-earthquake plan. To this aim, four seismic hazard models were developed for the city of Kalamata, according to stochastic simulation of the ground motion, using site amplification functions derived from ambient noise HVSR measurements. The structural vulnerability of the city was assessed following an empirical macroseismic model, developed for the European urban environment (EMS-98). The impact of the vulnerability due to the seismic hazard potential is also investigated by means of synthetic response spectral ratios at 108 sites of the city. The expected damage grade per building block, is calculated by combining vulnerability with the respective seismic intensities, derived for the four seismic sources. The importance of the followed methodology for implementing microzonation studies is emphasized, since the expected influence of the ground motion amplification due to local soil conditions has been approximated in detail. Moreover, new fragility curves for the main structural types in Kalamata are proposed for each seismic scenario.

Ground-Motion Attenuation, Stress Drop, and Directivity of Induced Events in the Groningen Gas Field by Spectral Inversion of Borehole Records

2020 ◽  
Vol 110 (5) ◽  
pp. 2077-2094 ◽  
Author(s):  
Gabriele Ameri ◽  
Christophe Martin ◽  
Adrien Oth
Keyword(s):  
Ground Motion ◽  
Destructive Interference ◽  
Rupture Directivity ◽  
Induced Earthquakes ◽  
Gas Field ◽  
Small Magnitude ◽  
Ground Motion Variability ◽  
Short Period ◽  
Groningen Gas Field ◽  
The Impact

ABSTRACT Production-induced earthquakes in the Groningen gas field caused damage to buildings and concerns for the population, the gas-field owner, and the local and national authorities and institutions. The largest event (ML=3.6) occurred in 2012 near Huizinge, and, despite the subsequent decision of the Dutch government to reduce the gas production in the following years, similar magnitude events occurred in 2018 and 2019 (ML=3.4). Thanks to the improvement of the local seismic networks in the last years, recent events provide a large number of recordings and an unprecedented opportunity to study the characteristics of induced earthquakes in the Groningen gas field and related ground motions. In this study, we exploit the S-wave Fourier amplitude spectra recorded by the 200 m depth borehole sensors of the G network from 2015 to 2019 to derive source and attenuation parameters for ML≥2 induced earthquakes. The borehole spectra are decomposed into source, attenuation, and site nonparametric functions, and parametric models are then adopted to determine moment magnitudes, corner frequencies, and stress drops of 21 events. Attenuation and source parameters are discussed and compared with previous estimates for the region. The impact of destructive interference of upgoing and downgoing waves at borehole depth on the derived parameters is also discussed and assessed to be minor. The analysis of the apparent source spectra reveals that several events show rupture directivity and provides clear observations of frequency-dependent directivity effects in induced earthquakes. The estimated rupture direction shows a good agreement with orientation of pre-existing faults within the reservoir. Our results confirm that rupture directivity is still an important factor for small-magnitude induced events, affecting the amplitude of recorded short-period response spectra and causing relevant spatial ground-motion variability.

scholarly journals Local and Moment Magnitude Analysis in the Ridgecrest Region, California: Impact on Interevent Ground-Motion Variability

2020 ◽  
Author(s):  
Dino Bindi ◽  
Riccardo Zaccarelli ◽  
Sreeram Reddy Kotha
Keyword(s):  
Ground Motion ◽  
Stress Drop ◽  
Ad Hoc ◽  
Epistemic Uncertainty ◽  
Earthquake Catalog ◽  
Motion Models ◽  
Ground Motion Model ◽  
Ground Motion Variability ◽  
Source Models ◽  
The Impact

ABSTRACT We investigate the dependence of event-specific ground-motion residuals in the Ridgecrest region, California. We focus on the impact of using either local (ML) or moment (Mw) magnitude, for describing the source scaling of a regional ground-motion model. To analyze homogeneous Mw, we compute the source spectra of about 2000 earthquakes in the magnitude range 2.5–7.1, by performing a nonparametric spectral decomposition. Seismic moments and corner frequencies are derived from the best-fit ω−2 source models, and stress drop is computed assuming standard circular rupture model. The Brune stress drop varies between 0.62 and 24.63 MPa (with median equal to 3.0 MPa), and values for Mw>5 are mostly distributed above the 90th percentile. The median scaled energy for Mw<5 is −4.57, and the low values obtained for the Mw 6.4 and 7.1 mainshocks (−5 and −5.2, respectively) agree with previous studies. We calibrate an ad hoc nonparametric ML scale for the Ridgecrest region. The main differences with the standard ML scale for California are observed at distances between 30 and 100 km, in which differences up to 0.4 magnitude units are obtained. Finally, we calibrate ground-motion models for the Fourier amplitude spectra, considering the ML and Mw scales derived in this study and the magnitudes extracted from Comprehensive Earthquake Catalog. The analysis of the residuals shows that ML better describes the interevent variability above 2 Hz. At intermediate frequencies (between about 3 and 8 Hz), the interevent residuals for the model based on Mw show a correlation with stress drop: this correlation disappears, when ML is used. The choice of the magnitude scale has an impact also on the statistical uncertainty of the median model: for any fixed magnitude value, the epistemic uncertainty is larger for ML below 1.5 Hz and larger for Mw above 1.5 Hz.

scholarly journals Seismic Fragility Analysis of High Earth-Rockfill Dams considering the Number of Ground Motion Records

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Congcong Jin ◽  
Shichun Chi
Keyword(s):  
Ground Motion ◽  
Fragility Curves ◽  
Damage Index ◽  
Fragility Analysis ◽  
Seismic Fragility ◽  
Settlement Rate ◽  
Earthquake Records ◽  
Rockfill Dam ◽  
Ground Motion Records ◽  
The Impact

This study analyzes the impact of the number of ground motions on the seismic fragility of a high earth-rockfill dam and the estimation of reasonable fragility parameters based on a sufficient number of earthquake records. In this paper, the vertical deformation is obtained using the three-dimensional finite element program DYNE3WAC combined with the Pastor–Zienkiewicz–Chan model and Biot dynamic consolidation theory. The relative seismic settlement rate is considered the damage index for the seismic fragility analysis of the dam. The fragility curves of the high earth-rockfill dam are determined by the multiple stripe analysis (MSA) method. A set of seismic waves is chosen based on the spectrum in the Chinese hydraulic structure seismic code. With an increasing number of earthquake records, the coefficients of variation (COV) of the mean and standard deviation (STD) of the relative seismic settlement rate decrease and tend to stabilize when the number of earthquake records reaches 34. The estimated fragility parameters θ and β are constant when the number of earthquake records exceeds 34. The requisite number of earthquake records for an accurate fragility estimation is determined by analyzing the lower and upper confidence intervals for the estimated θ and β. The 95% and 90% confidence interval can accurately estimate the fragility of a high earth-rockfill dam when the number of ground motion records reaches 36 and 32, respectively. The results of the fragility analysis demonstrate that the DYNE3WAC program and MSA method can provide an effective basis for determining fragility curves. Furthermore, the sensitivity analysis of earthquake records is essential for assessing the seismic fragility of high earth-rockfill dams.

Selection of random vibration theory procedures for the NGA-East project and ground-motion modeling

2021 ◽  
Vol 37 (1_suppl) ◽  
pp. 1420-1439
Author(s):  
Albert R Kottke ◽  
Norman A Abrahamson ◽  
David M Boore ◽  
Yousef Bozorgnia ◽  
Christine A Goulet ◽  
...  
Keyword(s):  
Ground Motion ◽  
Time Domain ◽  
Random Vibration ◽  
Amplitude Spectrum ◽  
Motion Modeling ◽  
Peak Response ◽  
Vibration Theory ◽  
Random Vibration Theory ◽  
The Time Domain ◽  
The Impact

Traditional ground-motion models (GMMs) are used to compute pseudo-spectral acceleration (PSA) from future earthquakes and are generally developed by regression of PSA using a physics-based functional form. PSA is a relatively simple metric that correlates well with the response of several engineering systems and is a metric commonly used in engineering evaluations; however, characteristics of the PSA calculation make application of scaling factors dependent on the frequency content of the input motion, complicating the development and adaptability of GMMs. By comparison, Fourier amplitude spectrum (FAS) represents ground-motion amplitudes that are completely independent from the amplitudes at other frequencies, making them an attractive alternative for GMM development. Random vibration theory (RVT) predicts the peak response of motion in the time domain based on the FAS and a duration, and thus can be used to relate FAS to PSA. Using RVT to compute the expected peak response in the time domain for given FAS therefore presents a significant advantage that is gaining traction in the GMM field. This article provides recommended RVT procedures relevant to GMM development, which were developed for the Next Generation Attenuation (NGA)-East project. In addition, an orientation-independent FAS metric—called the effective amplitude spectrum (EAS)—is developed for use in conjunction with RVT to preserve the mean power of the corresponding two horizontal components considered in traditional PSA-based modeling (i.e., RotD50). The EAS uses a standardized smoothing approach to provide a practical representation of the FAS for ground-motion modeling, while minimizing the impact on the four RVT properties ( zeroth moment, [Formula: see text]; bandwidth parameter, [Formula: see text]; frequency of zero crossings, [Formula: see text]; and frequency of extrema, [Formula: see text]). Although the recommendations were originally developed for NGA-East, they and the methodology they are based on can be adapted to become portable to other GMM and engineering problems requiring the computation of PSA from FAS.

High-frequency ground-motion variability for rough-fault ruptures  

2021 ◽  
Author(s):  
Jagdish Chandra Vyas ◽  
Martin Galis ◽  
Paul Martin Mai
Keyword(s):  
Ground Motion ◽  
Large Scale ◽  
Earthquake Ground Motion ◽  
Small Scale ◽  
Dynamic Rupture ◽  
Roughness Effects ◽  
Ground Shaking ◽  
Fault Surface ◽  
Fault Roughness ◽  
Ground Motion Variability

<p>Geological observations show variations in fault-surface topography not only at large scale (segmentation) but also at small scale (roughness). These geometrical complexities strongly affect the stress distribution and frictional strength of the fault, and therefore control the earthquake rupture process and resulting ground-shaking. Previous studies examined fault-segmentation effects on ground-shaking, but our understanding of fault-roughness effects on seismic wavefield radiation and earthquake ground-motion is still limited.  </p><p>In this study we examine the effects of fault roughness on ground-shaking variability as a function of distance based on 3D dynamic rupture simulations. We consider linear slip-weakening friction, variations of fault-roughness parametrizations, and alternative nucleation positions (unilateral and bilateral ruptures). We use generalized finite difference method to compute synthetic waveforms (max. resolved frequency 5.75 Hz) at numerous surface sites  to carry out statistical analysis.  </p><p>Our simulations reveal that ground-motion variability from unilateral ruptures is almost independent of  distance from the fault, with comparable or higher values than estimates from ground-motion prediction equations (e.g., Boore and Atkinson, 2008; Campbell and Bozornia, 2008). However, ground-motion variability from bilateral ruptures decreases with increasing distance, in contrast to previous studies (e.g., Imtiaz et. al., 2015) who observe an increasing trend with distance. Ground-shaking variability from unilateral ruptures is higher than for bilateral ruptures, a feature due to intricate seismic radiation patterns related to fault roughness and hypocenter location. Moreover, ground-shaking variability for rougher faults is lower than for smoother faults. As fault roughness increases the difference in ground-shaking variabilities between unilateral and bilateral ruptures increases. In summary, our simulations help develop a fundamental understanding of ground-motion variability at high frequencies (~ 6 Hz) due small-scale geometrical fault-surface variations.</p>

Within- and Between-Event Variabilities of Strong-Velocity Pulses of Moderate Earthquakes within Dense Seismic Arrays

2021 ◽  
Author(s):  
Ming-Hsuan Yen ◽  
Sebastian von Specht ◽  
Yen-Yu Lin ◽  
Fabrice Cotton ◽  
Kuo-Fong Ma
Keyword(s):  
Ground Motion ◽  
Structural Engineering ◽  
Strike Slip ◽  
Physical Factors ◽  
Velocity Amplitude ◽  
Seismic Arrays ◽  
Directivity Effect ◽  
Forward Directivity ◽  
Significant Damage ◽  
The Impact

ABSTRACT Ground motion with strong-velocity pulses can cause significant damage to buildings and structures at certain periods; hence, knowing the period and velocity amplitude of such pulses is critical for earthquake structural engineering. However, the physical factors relating the scaling of pulse periods with magnitude are poorly understood. In this study, we investigate moderate but damaging earthquakes (Mw 6–7) and characterize ground-motion pulses using the method of Shahi and Baker (2014) while considering the potential static-offset effects. We confirm that the within-event variability of the pulses is large. The identified pulses in this study are mostly from strike-slip-like earthquakes. We further perform simulations using the frequency–wavenumber algorithm to investigate the causes of the variability of the pulse periods within and between events for moderate strike-slip earthquakes. We test the effect of fault dips, and the impact of the asperity locations and sizes. The simulations reveal that the asperity properties have a high impact on the pulse periods and amplitudes at nearby stations. Our results emphasize the importance of asperity characteristics, in addition to earthquake magnitudes for the occurrence and properties of pulses produced by the forward directivity effect. We finally quantify and discuss within- and between-event variabilities of pulse properties at short distances.

Three-Dimensional Simulations of Strong Ground Motion in the Shidian Basin

2014 ◽  
Vol 501-504 ◽  
pp. 1447-1452
Author(s):  
Yan Yan Yu ◽  
Qi Fang Liu
Keyword(s):  
Surface Wave ◽  
Ground Motion ◽  
Seismic Waves ◽  
Three Dimensional ◽  
Spectral Element ◽  
Low Velocity ◽  
Computing Technique ◽  
Soil Deposits ◽  
Basin Edge ◽  
The Impact

Seismic response of the Shidian basin to moderate scenario earthquake is investigated considering 3D basin model incorporated with real topography by using the spectral-element method and parallel computing technique. The wave propagation process, the generation of surface wave, and the impact of soil deposits velocity to the basin-induced surface wave are studied in this paper. The results show that the amplification behavior of the basin is the interactions of basin geometry and low velocity soil deposits. First, locally small hollows in the basin are apt to trap seismic waves and produce much stronger ground motion, basin edge and areas with deep sediments are also characterized with large amplification. Then, basin with softer soil deposits produces stronger surface waves with lower propagation velocity and higher mode.

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